1. Field of the Invention
This invention is directed to a skin cream containing allantoin in an oil-in-water emulsion with improved stability.
2. General Background and State of the Art
Allantoin is a commonly used ingredient in cosmetic applications, particularly for skin creams, where it exerts a skin protective function. Many-such cosmetic compositions and other compositions are prepared as emulsions, particularly oil-in-water emulsions. One emulsifier system used with such compositions is a combination of sodium lauryl sulfate and beeswax. Although solutions of sodium lauryl sulfate are alkaline with an approximate pH of 9.5, the simultaneous use of beeswax with its organic acids produces a complex and neutralized system with a pH of about 6.8 to about 7.5. However, in such a system with a pH range of 6.8 to 7.5, allantoin degrades significantly with time and in accelerated stability tests at 40° C. Because cosmetics and other preparations designed for application to the skin are typically stored by users at room temperature, and room temperatures can fluctuate with climatic conditions, such a degree of stability is undesirable. Therefore, there is a need for an oil-in-water emulsified composition containing allantoin in which the stability of allantoin is increased.
In particular, there is a need for compositions that are suitable for treating a number of severe and difficult-to-treat skin conditions. One of these skin conditions is epidermolysis bullosa. This is a severe genetic skin disorder in which the skin breaks down and large blisters appear. These blisters are difficult to treat by conventional means. Other skin diseases for which improved treatments are needed are pressure ulcers, decubitus ulcers or bed sores, and diabetic ulcers, and milia, as well as other conditions affecting the skin and having an inflammatory component such as eczema, urticaria, atopic dermatitis, contact dermatitis, arthritis, gout, and lupus erythematosus. Therefore, improved compositions that are suitable for treating these diseases are needed.